\begin{tikzpicture}
	\pgfmathsetmacro{\r}{2}
	\tkzDefPoints{0/0/O, \r/0/A}
	\tkzDefPoint(30:\r){B}
	\tkzDefPoint(70:\r){C}
	\tkzDefPoint(130:\r){D}

	\tkzDrawSegments(O,A  O,B  O,C  O,D)
	\tkzLabelPoints[below](A, O)
	\tkzLabelPoints[right](B, C, D)
\end{tikzpicture}

